Descenders are widely used in the field of rope access and rescue for controlling the descent of people or equipment suspended by rope. Descenders are commonly used by operators to descend down a rope that is affixed overhead. Descenders may also be attached to an anchor position to allow an operator to control the descent of one or more people or gear from a remote location. Typically, descenders are comprised of elements that clamp or pinch the rope and are self-energized by load applied to the rope in one direction through the device. Controlled release is typically achieved by actuation of a lever which alleviates the clamping force holding the rope, allowing controlled release of rope through the device. Under certain circumstances it is necessary to pull rope through the descender, thereby reversing the direction of travel. In these cases the descender serves as a turning point for the rope and a means of progress capture.
Descenders commonly incorporate a “panic” safety feature such that if the means of release is inadvertently actuated too far, the descender will cease the release of rope, preventing an uncontrolled freefall of the suspended persons or equipment.
Descenders that are currently available have some recognized limitations. Compact descenders of the type that would be worn on a harness do not excel at handling the greater loads involved with a two person descent, as is common in a rescue situation. The maximum working load specification of commonly available descenders does not accommodate requirements of two person rescue, or requires additional hardware to configure the device for high loads. The effort required to initiate release at higher loads is difficult, and controllability is diminished. At these higher loads, descenders commonly have the undesirable effect of flattening the rope or milking the rope sheath due to the aggressive localized pinching employed to grip the rope. Additionally, compromises made to make the device perform well over a wide range of loads contribute to poor performance at low loads. For example, a user may find difficulty initiating descent of a light weight load due to high friction in the device, or may find that the release is initiated at a handle position very near the point of panic relock, making operation frustrating.
As such, there is a need for a compact descender capable of managing a large range of loads while maintaining easy and controlled release.